Method of inserting a close-fitting flexible heater element into an armored passage



March 5, 1963 H. J. LOEHLEIN ETAL INVENTORS HAQ OLD \J. LOEH LEIN HUBEFZT G. HUBER W X/W ATTORNEYS United rates 3,079,673 METHOD GE INSERTING A (ILOSE-FITTHNG FiiEX- IBLE HEATER ELEMENT INKG AN ARMGRED PASSAGE Harold J. Loehlein and Hubert G. Huber, Louisville, Ky., assignors to Reynolds Metals Company, Richmond, Va., a corporation otDelaware Filed June 4, 1958, Ser. No. 739,848 Claims. ((31. 29-4555) This invention relates to articles having insulated electrical heating elements housed within an interior passage therein and to a method for installing such elements.

I Various. forms of heating appliances such as skillets, heating pans and the like are formed of metallic sheet rnaterial in which an interior passage is provided for reception of a heater element. Such passages are usually of elongated form and with a curved or tortuous path in order to disperse the heating effect of the element. Of particular significance, the space between the insulation of the heator element and the surface of the metallic armored passage is minimized for the purpose of achieving the most efficient heat transfer. The resulting close fit of the element in such passage has thus given rise to tedious and relatively expensive procedures for installing the heater element. In general, the present practice is to push a thin wire or the like through such passage, attach one end of the wire to'the heating element, and then slowly pull the heating element under tension into place. When, however, the desired close fit is attempted and the passage is curved, considerable frictional resistance is set up between the insulation of the elementand the inner walls of the passage, thus slowing the operation and in some cases endangering the integrity of the insulation.

.- It is a'purpose of our invention to provide a simple, inexpensive, and rapid method for installing such heater elements in armored passages without experiencing the difficulties inherent in the present practices.

An object of the invention is to provide an improved method for inserting a close-fitting flexible heater unit into an armored passage.

Another object is to provide an improved apparatus for'in'serting a close fitting flexible heater unit into an armored passage.

A further object is to provide an improved heating appliance having a close fit between a heater element housed within a passage in the appliance and the surface of the passage, in order to insure an efficient heat transfer.

Still a further object is to provide an improved method for fabricating heating appliances.

' Other obiects and advantages of the invention will become more apparenflwhen the following description is considered in conjunction with the accompanying drawings in which: I

v HQ. 1 is a diagrammatic view of one arrangement of apparatus during the insertion of the heater element in the armored passage;

FIG. 2, is a longitudinal sectional view to an enlarged scale, through the holder and with the seal shown detached, and with the heater element shown in elevation;

FIG. 3 is a sectional view taken on line 3-3 of FIG. 2;

FIG. 4 is an end elevation of the seal taken on line 4-4 of FIG. 2;

FIG. 5 is a detail view in section showing one form of quick-disconnect coupling for the holder;

FIG. 6 is a perspective view showing the armored Inetallic article during insertion of the heater element; and

FIG. 7 is a sectional view taken on line 7-7 of PEG. 6, and to an enlarged scale.

In accordance with our invention we take advantage of the vibration caused in a flexible heater element as a stream Patented Mar. 5, 1&8?

of fluid is passed thereover at high speed while the element is closely confined in a space slightly larger than the element in cross-section. This vibration serves to reduce the frictional resistance of the element with the walls confining the same, to a much lower value than when the element is pulled under tension along those walls. At the same time the element itself during its vibration is forced or carried by the moving fluid along the confining space and thus may be cmplaced in the desired location without requiring any tension to be applied thereto.

Referring now to FIG. 1 there is shown a typical metallie sheet 10 which, for example, may be made of aluminum. This sheet which preferably has been fabricated into the form in which it will be employed in the heating appliance (a rectangular sheet being shown here merely for illustrative purposes) contains an elongated open-ended passage with a bulged-out wall 11 and having a first end 12 and a second end 13. Such a sheet may be formed by any of the well known processes wherein two flat portions of the metal are bonded together to form an integral sheet except at a predetermined location where a passage is to I be formed by subsequent internal application of a pressure fluid which bulges out one or more of those confronting sheets to form a passage space. As seen in FIG. 7, the passage has an open space is beneath the wall 11 and between the bonded-together portions of the sheet. The space 14 has a minimum transverse dimension slightly larger than the maximum transverse dimension of the heater element so that the element'is inserted with a close fit. Moreover, the wall portion 11 is thin enough to be readily deformable so that after the heater element is inserted, that wall may be pressed into physical contact with a substantial portion of the surface of that element thereby to give a good heat transfer, and at the same time to" provide an armored protection for the more fragile heater element.

In order to disperse the heating efiect more uniformly over the planar surface of the appliance, the passage is generally formed in a tortuous path, here shown as a U-shaped path, although other forms of path, either straight or substantially fully circular may be used. As will be apparent, the more curved the path is, the greater is the difiiculty in inserting the heater element by conventional practices, due largely to frictional resistance.

Referring now to FIG. 2, in accordance with our invention, we provide an elongated tubular holder 243 which preferably is straight and which has a length substantially equal to the length of the heater element itself. The heat er element shown at 21 may be any of several conventional types, being characterized by its flexibility, its inorganic insulation, and its high resistance wire embedded in that insulation. One suitable form comprises a nickel-chrome wire wound in helical form and embedded in glass fibre. As seen in FIG. 3, the heater element is slightly smaller in cross-section than is the internal space within that holder, for example, a cylindrical element having an outside diameter of 0.25 inch being suitable for use with a cylindrical holder having an internal diameter of 0.375 inch.

Thus when the element is inserted endwise into the holder preparatory to insertion into the sheet, no dificulty is experienced in loading the holder, but after being loaded, the heater element due to its flexible nature rests in an undulatory form within that holder.

At one end, the holder is preferably tapered in arcuate form, as at 2'2, to correspond to the general configuration of the end of passage space 14. At its other end, the

holder may conveniently be provided with a threaded,

system. A suitable gasket 25 may be disposed within the coupling 24 and against which the holder abuts durmg the application of full pressure. From coupling 24 a conduit 26 having a suitable control valve 27 therein extends to a reservoir 28 of pressure fluid. Various types of pressure fluid under various pres-sures may be used, but we have found that in general a supply of air maintained at about 3G0 pounds per square inch is satisfactory for inserting a conventional heater element rapidly into a passage such as described.

While not always essential, we also have found that the operation maybe conducted with less noise if We provide a suitably shaped hollow seal 30 for interposition between the end 22 of the holder and the open end of the passage in the sheet. This seal, which may be conveniently formed of rubber, is readily detachable and not only reduces noise, but also serves to reduce vibration fatigue on the operator holding the .holder 20 and to conserve the amount of pressure fluid employed.

Having thus described the combination of the apparatus used with our invention, the method of operation will now be apparent. The heater element is first loaded into the holder and if the seal is used,.it is then emplaced at the appropriate end of the holder. The loaded holder is then connected to the coupling by a simple rotary move ment and the opposite end of the coupled and loaded holder is held firmly in position against one of the ends 12 or 13 of the passage in the sheet. Thereupon valve Z7 is manipulated and pressure fluid immediately rushes through the holder and the passage in the sheet. As it moves through the holder .it encounters a non-uniform obstruction from the heater element and a turbulent flow results, causing various parts of the heater element to receive a pressure impulse from that moving fluid. Since the elementis flexible, or at least semi-flexible, it is vibrated, and during its vibration is physically moved by entrainment with the moving fluid. As a significant feature, the vibration of the element as it moves causes much less abrasive wear thereon than is the case whenit is pulled under tension along contacting walls of the passage. It is found that the element may be emplaced in position within the sheet in a remarkably short time, for example, about 4-6 seconds for an elementabout 24 inches long entering a U-shaped passage as illustrated.

Upon insertion of the element, the valveis closed, the holder disconnected from the coupling and a reloading of the holder for the next operation is carried out. After the heater element is fully inserted in the passage, the deformable wall 11 of the passage is pressed by any suitable means into close contact with the heater element which has been inserted as above described.

Having thus described our invention, it will be understood that numerous changes may be made in the construction without departing from the spirit of the 'inven tion and it is, therefore, desired that the present embodiment be considered in all respects as illustrative and not restrictive reference being made to the appended claims rather than to the foregoing description to indicate the scope of the invention.

We claim:

1. In the art of fabricating heating appliances the steps comprising, providing a sheet of metallic material having an elongated open-ended passage of a uniform cross sectional area formed therein and disposed in a tortuous munic'ation with said one end of said passage, vibrating said element by introducing a fluid under super atmos pheric pressure from the other end of said holder and lengthwise of said element into and through said passage, and continuin'g to introduce said fluid pressure into said passage while simultaneously causing the resulting fluid stream to eject said element with a vibratory movement from said holder into said passage, thereby to emplace said element within said passage without damaging said insulation.

2. The method of claim 1 including, reducing the cross sectional area of said passage following emplacement of.

than that of said passage and with said elementconfined loosely within an elongated hollow holder having one end in sealing contact with said one end of said passage, vibrating said element by introducing a fluid under superatmosphcric pressure from the other end of said holder and lengthwise of said element into and through-said pass sage, and continuing said fluid pressure while simultaneously causing the resulting fluid stream to eject said element with a vibratory movement from said holder into said passage, thereby to emplace said element within said' passage without damaging said insulation.

4. A method of inserting a flexibla'insulated'conjductor into a hollow passageway inwhich the flexibla'ing sulated conductor has across sectionalarea substantially as large as the cross sectional area of said hollow passageway comprising: providing a sheet of metallic material having an elongated open-ended passageway o f i form cross sectional area formed therein and disposed in a tortuous path in the plane of said sheet, confining a flexible, insulated conductor having across sectional. area substantially as large as t at .Of said passageway within an elongated hollow holder which provided with one tapering end portion, placing the'tapering end of said hollow holder adjacent and in fluid communication with the open end of said passageway, vibrating said flexible, insulated conductor by introducing a fluid under 7 super-atmospheric pressure from the other en of said holder, throttling said fluid pressure through the tapered end of said holder, and continuing to introduce saidfluid pressure into said passageway thereby causing the result-' ing fluid stream to eject said flexible insulated conductor with a vibratory movement from said holder into said passageway and thereby emplacing said flexible,vinsulated conductor within said passageway without damaging said insulation. I

5. A method of inserting a flexible, insulated conductor into a hollow passageway in which the flexible, insulated conductor has a cross sectional area substantially as large as the cross sectional area of .saidhollow passageway comprising: providing a sheet of metallic material having an elongated open-ended passageway of uniform cross sectional area formed therein and disposed .in a tortuous path in the plane of said sheet, placing va flexible, insulated conductor having a cross sectional areasubstantially as large as that of said passageway within an'elongated hollow holder which is provided with one tapering end portion, sealing the tapering end ofv said hollow holder in fluid communication with the open end of said passageway, suspending said flexible, insulated conductor by admitting a fluid under super-atmospheric pressure into said holder, driving said flexible,,insulated conductor toward the tapering end of said holderlby the direction of admittance of said fluid pressure, throttling said fluid pressure through the tapering end of said holder, and continuing the admittance of said fluidpressure into said passageway thereby causing the resulting fluid stream to eject said flexible, insulated conductor intosaidpassagea way.

(References on following page) References Cited in the file of this patent UNITED STATES PATENTS Jessup Mar. 29, 1932 6 Oakley May 4, 1954 Bunnell et a1. Feb. 11, 1958 Kjellsen July 15, 1958 Schurman Jan. 20, 1959 Janos Jan. 12, 1960 

1. IN THE ART OF FABRICATING HEATING APPLIANCES THE STEPS COMPRISING, PROVIDING A SHEET OF METALLIC MATERIAL HAVING AN ELONGATED OPEN-ENDED PASSAGE OF A UNIFORM CROSS SECTIONAL AREA FORMED THEREIN AND DISPOSED IN A TORTUOUS PATH IN THE PLANE OF SAID SHEET, ARRANGING IN END-TO-END RELATION WITH ONE END OF SAID PASSAGE AN ELONGATED, FLEXIBLE, INSULATED HEATING ELEMENT HAVING A UNIFORM CROSS SECTIONAL AREA ONLY SLIGHTLY LESS THAN THAT OF SAID PASSAGE AND WITH SAID ELEMENT CONFINED LOOSELY WITHIN AN ELONGATED HOLLOW HOLDER HAVING ONE END DISPOSED IN FLUID COMMUNICATION WITH SAID ONE END OF SAID PASSAGE, VIBRATING SAID ELEMENT BY INTRODUCING A FLUID UNDER SUPER-ATMOSPHERIC PRESSURE FROM THE OTHER END OF SAID HOLDER AND LENGTHWISE OF SAID ELEMENT INTO AND THROUGH SAID PASSAGE, AND CONTINUING TO INTRODUCE SAID FLUID PRESSURE INTO SAID PASSAGE WHILE SIMULTANEOUSLY CAUSING THE RESULTING FLUID STREAM TO EJECT SAID ELEMENT WITH A VIBRATORY MOVEMENT FROM SAID HOLDER INTO SAID PASSAGE, THEREBY TO EMPLACE SAID ELEMENT WITHIN SAID PASSAGE WITHOUT DAMAGING SAID INSULATION. 